// DecaDuinoTWR_client
// A simple implementation of the TWR protocol, client side
// Contributors: Adrien van den Bossche, Réjane Dalcé, Ibrahim Fofana, Robert Try, Thierry Val
// This sketch is a part of the DecaDuino Project - please refer to the DecaDuino LICENCE file for licensing details
// This sketch implements the skew correction published in "Nezo Ibrahim Fofana, Adrien van den Bossche, Réjane
// Dalcé, Thierry Val, "An Original Correction Method for Indoor Ultra Wide Band Ranging-based Localisation System"
// https://arxiv.org/pdf/1603.06736.pdf

#include <SPI.h>
#include <DecaDuino.h>

// Timeout parameters
#define TIMEOUT_WAIT_START_SENT 5 //ms
#define TIMEOUT_WAIT_ACK 10 //ms
#define TIMEOUT_WAIT_DATA_REPLY 20 //ms

// Ranging period parameter
#define RANGING_PERIOD 500 //ms

// TWR client states state machine enumeration: see state diagram on documentation for more details
enum { TWR_ENGINE_STATE_INIT, TWR_ENGINE_STATE_WAIT_START_SENT, TWR_ENGINE_STATE_MEMORISE_T1,
TWR_ENGINE_STATE_WAIT_ACK, TWR_ENGINE_STATE_MEMORISE_T4, TWR_ENGINE_STATE_WAIT_DATA_REPLY, 
TWR_ENGINE_STATE_EXTRACT_T2_T3 };

// Message types of the TWR protocol
#define TWR_MSG_TYPE_UNKNOWN 0
#define TWR_MSG_TYPE_START 1
#define TWR_MSG_TYPE_ACK 2
#define TWR_MSG_TYPE_DATA_REPLY 3

uint64_t t1, t2, t3, t4;
uint64_t mask = 0xFFFFFFFFFF;
int32_t tof;

DecaDuino decaduino;
uint8_t txData[128];
uint8_t rxData[128];
uint16_t rxLen;
int state;
uint32_t timeout;


void setup()
{
  pinMode(13, OUTPUT); // Internal LED (pin 13 on DecaWiNo board)
  Serial.begin(115200); // Init Serial port
  SPI.setSCK(14); // Set SPI clock pin (pin 14 on DecaWiNo board)

  // Init DecaDuino and blink if initialisation fails
  if ( !decaduino.init() ) {
    Serial.println("decaduino init failed");
    while(1) { digitalWrite(13, HIGH); delay(50); digitalWrite(13, LOW); delay(50); }
  }

  // Set RX buffer
  decaduino.setRxBuffer(rxData, &rxLen);
  state = TWR_ENGINE_STATE_INIT;

  // Print top table colomns
  Serial.println("ToF\td\tToF_sk\td_sk");
}

void loop()
{
  float distance;
  
  switch (state) {
   
    case TWR_ENGINE_STATE_INIT:
      delay(RANGING_PERIOD); // Wait to avoid medium flooding between two rangings or if a ranging fails
      decaduino.plmeRxDisableRequest();
      Serial.println("New TWR");
      txData[0] = TWR_MSG_TYPE_START;
      decaduino.pdDataRequest(txData, 1);
      timeout = millis() + TIMEOUT_WAIT_START_SENT;
      state = TWR_ENGINE_STATE_WAIT_START_SENT;
      break;

    case TWR_ENGINE_STATE_WAIT_START_SENT:
      if ( millis() > timeout ) {
        state = TWR_ENGINE_STATE_INIT;
      } else {
        if ( decaduino.hasTxSucceeded() ) {
          state = TWR_ENGINE_STATE_MEMORISE_T1;
        }
      }
      break;

    case TWR_ENGINE_STATE_MEMORISE_T1:
      t1 = decaduino.getLastTxTimestamp();
      timeout = millis() + TIMEOUT_WAIT_ACK;
      decaduino.plmeRxEnableRequest();
      state = TWR_ENGINE_STATE_WAIT_ACK;
      break;

    case TWR_ENGINE_STATE_WAIT_ACK:
      if ( millis() > timeout ) {
        state = TWR_ENGINE_STATE_INIT;
      } else {
        if ( decaduino.rxFrameAvailable() ) {
          if ( rxData[0] == TWR_MSG_TYPE_ACK ) {
            state = TWR_ENGINE_STATE_MEMORISE_T4;
          } else {
          	decaduino.plmeRxEnableRequest();
          	state = TWR_ENGINE_STATE_WAIT_ACK;
          }
        }
      }
      break;

    case TWR_ENGINE_STATE_MEMORISE_T4:
      t4 = decaduino.getLastRxTimestamp();
      timeout = millis() + TIMEOUT_WAIT_DATA_REPLY;
      decaduino.plmeRxEnableRequest();
      state = TWR_ENGINE_STATE_WAIT_DATA_REPLY;
      break;

    case TWR_ENGINE_STATE_WAIT_DATA_REPLY:
      if ( millis() > timeout ) {
        state = TWR_ENGINE_STATE_INIT;
      } else {
        if ( decaduino.rxFrameAvailable() ) {
          if ( rxData[0] == TWR_MSG_TYPE_DATA_REPLY ) {
            state = TWR_ENGINE_STATE_EXTRACT_T2_T3;
          } else {
            decaduino.plmeRxEnableRequest();
          	state = TWR_ENGINE_STATE_WAIT_DATA_REPLY;
          }
        }
      }
      break;

    case TWR_ENGINE_STATE_EXTRACT_T2_T3:
      t2 = decaduino.decodeUint40(&rxData[1]);
      t3 = decaduino.decodeUint40(&rxData[6]);
      tof = (((t4 - t1) & mask) - ((t3 - t2) & mask))/2;
      distance = tof*RANGING_UNIT;
      Serial.print(tof);
      Serial.print("\t");
      Serial.print(distance);
      tof = (((t4 - t1) & mask) - (1+1.0E-6*decaduino.getLastRxSkew())*((t3 - t2) & mask))/2;
      distance = tof*RANGING_UNIT;
      Serial.print("\t");
      Serial.print(tof);
      Serial.print("\t");
      Serial.println(distance);
      state = TWR_ENGINE_STATE_INIT;
      break;

    default:
      state = TWR_ENGINE_STATE_INIT;
      break;
  }
}